406ci Engine Rebuild - Top It Off!

We bring new life to a once-tired 406ci

This 406 normally is at home in between the fenders of a ’67 Nova. After years of feeding nitrous through it, we decided to give the engine a simple makeover by swapping out the old pieces in exchange for a complete bolt-on system from Trick Flow Specialties.

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Taking a closer look at the original mill, this gem was pieced together on a tight swap meet budget and relied on a liberal shot of nitrous to catch any would-be challengers at the local grudge night sessions. It featured an old set of cast-iron heads, a Quadrajet carb, a flat tappet camshaft we borrowed, and a set of stamped-steel roller-tipped rocker arms.

For this month, we left the short-block alone with its factory 5.56-inch rods and cast 400 crankshaft. We figured it was the perfect candidate for a top end upgrade and comes complete with everything being supplied to transform our little sleeper. We should mention that Trick Flow Specialties offers each of the items used here individually, however we took the easier route and ordered the all-in-one package.

This particular kit included a pair of TFS’ Super 23 aluminum cylinder heads, and comes with the cam and lifters, all the necessary gaskets, pushrods, full roller 1.5:1 ratio rockers, and a new double-roller timing chain. To finish up the order, we also went with a Quick Fuel Technology 750-cfm carburetor and a Weiand Speed Warrior dual-plane intake manifold.

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We didn’t want to turn this into an all-out track piece; on the contrary, we wanted to keep its street manners intact and decided on a mild hydraulic flat tappet camshaft, spec’d out at 228/234 degrees of duration and 0.480/0.494 lift with a 110 LSA. The Trick Flow Specialties Super 23 195 heads come standard with a 62cc chamber, which produced a pump gas–friendly 9.7:1 compression with our dish pistons.

To document our changes, we headed over to The Carb Shop in Ontario, California, where we baselined the original setup and put the new combination to the test. The baseline figures were modest at 324 hp, but did surprisingly well in the torque department with 439 lb-ft. With the first set of numbers secured, we took a couple of hours to swap over to our new combo and found a significant improvement with an increase to 409 hp and 471 lb-ft! Now for the fun part, seeing how the Nova reacts with an additional 150-shot of nitrous . . . stay tuned.

MORE PHOTOS

With our engine strapped to The Carb Shop’s DTS engine dyno, we made a couple of baseline pulls with the best results being 324 hp and 439 lb-ft.

With our engine strapped to The Carb Shop’s DTS engine dyno, we made a couple of baseline pulls with the best results being 324 hp and 439 lb-ft.

This engine had a few upgrades over the years, one of them being these roller tipped, stamped steel rocker arms.

Once the valve covers and distributor were removed, we were able to take off the intake and carburetor.

Next, we removed the head bolts and pulled off the old cast-iron cylinder heads. From a weight standpoint, we were able to shed roughly 45 pounds by swapping over to the Super 23 cylinder heads.

Next, we removed the head bolts and pulled off the old cast-iron cylinder heads. From a weight standpoint, we were able to shed roughly 45 pounds by swapping over to the Super 23 cylinder heads.

After removing the harmonic balancer, including the timing cover and chain, we were able to remove the old bumpstick.

With the old camshaft out, we made sure we had the No. 1 cylinder at TDC using a dial indicator.

Moving on to the fun part, we made sure to use plenty of assembly lube on all of the COMP camshaft lobes.

After the cam and new timing chain were installed, we degreed the cam to make sure we had it installed properly. Following COMP’s recommendation, we placed the cam straight up after verifying the numbers on the degree wheel.

Next, we dropped in the new hydraulic lifters.

If you have a tendency to forget items during the initial order, you’ll appreciate the TFS top end package; each system comes complete with all the necessary fasteners and gaskets required.

With the head gaskets installed, we moved onto the new TFS Super 23 cylinder heads.

Using the supplied head bolts, we torque the heads down in their respective order to 65 ft-lb. The heads come with 2.02/1.60-inch intake/exhaust valves and available in your choice of 62cc or 72cc chambers. You also get to select from several valvespring options, making it easy to accommodate your combination.

With the heads installed, we dropped in the 7.850-inch length pushrods and the 1.5:1 ratio rockers.

Once the intake gaskets were set in place, we installed the Weiand dual-plane Speed Warrior intake manifold. Each bolt was torqued to 25 ft-lb.

We reused the original GM HEI distributer, cap, and wires.

To top it off, we went with a Quick Fuel Technology 750-cfm mechanical secondary carburetor. This Street/Strip version is also offered in a 650, 750, and 830 cfm rating with your choice of mechanical or vacuum secondaries.

Our finished product not only looks better, but we increased our horsepower to 409 and our torque to 471. That’s an 85hp increase and 32 lb-ft of torque. Not bad for a few hours worth of work.

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